Look at the sticky Mysterious Extra Stitches
. Since the edges are garter stitch, you might be getting them when you start a row. If the yarn is over the top of the needle it pulls up the edge st and the 2 legs look like separate stitches. The other place could be when you transition from the knit to purl sts or purl to knit on the WS rows; make sure you bring the yarn between the needles and not over the top.